Substance abuse among homeless youth is twice the rate for school youth. In addition to being at greater risk for AIDS, homeless youth also report a broader range of substance-related problems, generally at higher levels of severity. A majority of homeless youth, however, do not receive substance abuse treatment. A recent study indicated that only 30 percent of homeless youth utilize even basic shelter services. Simply increasing ongoing substance abuse treatment for this population will not address the multiple problems these youth face. Few such interventions exist, and of the programs in operation, none have documented treatment outcome. In addition, few assessment instruments have documented validity or reliability with this population. The purpose of this study is to adapt a highly effective intervention for homeless adults to meet the special needs of homeless youth. Development of a manual guided therapy based upon the Community Reinforcement Approach (CRA) will be followed by recruitment and randomization to one of two interventions: (1) service as usual (no treatment control), and (2) CRA individual therapy and HIV intervention. The first 30 participants into the project will be asked to participate in a test-retest study of several of the assessment instruments. The efficacy of CRA and HIV intervention tailored for homeless youth will be evaluated and documented 3 and 6 months after treatment, and will include measures of substance use, HIV risk behaviors, negative affect, social stability, and related problem behaviors. Differential treatment response as a function of ethnicity, sexual orientation, and gender will be investigated to better understand the intervention.